The aim of this work is to ascertain the very low density human serum lipoprotein apoprotein and subpopulation composition of normal and hyperlipoproteinemic individuals, and to determine the concentration fluctuations as a function of food intake. Lipoproteins will be isolated by preparative ultracentrifugation, apoproteins by chromatographic procedures. Subpopulations will be determined by a new radioimmunoassay.